[Pw_forum] Oxygen molecule binding energy

[elbuesta at icqmail.com]

 Dear all,


I recently evaluated with PW the binding energy of a O2 molecule using the regular ultra-soft PP from the webpage. I noticed that the energy obtained could be 5.7eV or 6.7eV depending if the flag "nosym=.true." is used or not in the  energy evaluation of the isolated oxygen atom. I would like to know if anyone could help me understand why such a large difference is obtained for this system, since for many other systems (such as metals) the inclusion of "nosym=.true." for the isolated atom do not affect so much (or not at all) the value of the binding/cohesive energy. 


Thanks very much for your time, and all best for all!

Fabio Negreiros
IPCF - CNR, Pisa - Italia

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